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The manganese-tetrasulfonatophthalo-cyanine (MnTSPc) catalyzed luminol-hydrogen peroxide chemiluminescence (CL) system can be quenched in the presence of nucleic acids. A new and highly sensitive CL quenching method for determining nucleic acids in aqueous solutions has been developed. Under optimum conditions, linear relationships were found between the quenched intensity of CL and the concentration of nucleic acids in the range 0.10–2.0 µg mL-1 for calf thymus DNA and 0–1.6 µg mL-1 for fish sperm DNA. The limits of detection were 14.8 ng mL-1 for calf thymus DNA and 21.7 ng mL-1 for fish sperm DNA. The relative standard deviation (RSD) of nine replicate measurements is 1.4% for 1.0 µg mL-1 calf thymus DNA. The method was applied to the analysis of nucleic acids in synthetic samples and the results are satisfactory. [ABSTRACT FROM AUTHOR]

Highlights • A novel method for the sensing of H 2 O 2 and choline was developed. • The detection was based on near infrared luminescent UCNPs. • The upconversion luminescence was quenched to 3% of its original intensity by Fe3+. • UCNPs can avoid the interference of fluorescent substances in complex samples. Abstract Choline is an essential nutrient for the growth and development of the baby, and therefore it is often added to infant formula. In this paper, a novel sensor for choline determination in infant formula is developed based on upconverting nanoparticles (UCNPs) with near infrared luminescence. UCNPs-based detection can avoid the interference of background fluorescence from complex samples, and thus provide high selectivity and sensitivity. It was observed that in the presence of Fe3+, polyacrylic acid coated UCNPs were quenched to 3% of its original intensity. The degree of quenching was among the best for UCNPs. Hydrogen peroxide could oxidize Fe2+ to Fe3+, which caused quenching of the upconversion luminescence. A new H 2 O 2 detection method was thus established. In addition, choline could be hydrolyzed to betaine by choline oxidase, and at the same time produced H 2 O 2 , which also caused luminescence quenching through Fe2+ oxidation. Therefore, selective choline sensing was achieved. [ABSTRACT FROM AUTHOR]